1. Field of the Invention
The present invention relates to a capacitance measurement device, and to a capacitance-type planar sensor apparatus and capacitance-type liquid-level detector apparatus that use the measurement device.
2. Description of the Related Art
A device, which judges whether or not a change in capacity to be measured arises from an event making an object to be detected, is set forth in International Publication No. 2011/004727 (or Patent Literature No. 1) The device is equipped with: a first switch, which serially connects a reference capacity “Cs” with respect to a capacity “Cx1” to be measured to a first potential source “V1” side and one of whose opposite ends is put in place between the opposite ends of the reference capacity connected to the first potential source “V1”; a second switch, one of whose opposite ends is put in place between another one of the opposite ends of the to-be-measured capacity connected to a second potential source or a free space and another one of the opposite ends of said reference capacity; and a third switch, which is put in place between the opposite ends of said to-be-measured capacity.
And, a number of repetitive operations until the potential between the terminals of the reference capacity “Cs” changes to a set-up potential “Vref” is counted when an operation to turn the second switch to the closed state and another operation to turn the third switch to the closed state are repeated alternately after a first-switch operation that turns the first switch to the closed state and then turns it to the opened state. And, whether or not a change in the to-be-measured capacity arises from an event making an object to be measured is judged based on the respective number of repetitive operations (“N1,” “N2”) when varying a time for carrying out the second-switch operation.
Moreover, opposing multiply-lined electrodes to multiply-columned electrodes to measure the respective capacitances at the matrix-shaped measurement-objective positions is set forth in Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2005-30901 (or Patent Literature No. 2). The device measures the capacitances by measuring a current, which flows to one of the capacitances at the measurement-objective positions, when outputting a pulsating signal to another one of the capacitances thereat.
Moreover, measurement devices for capacitance are set forth in Japanese Patent Gazette No. 3379388 (or Patent Literature No. 3), Japanese Patent Gazette No. 2561040 (or Patent Literature No. 4), International Publication No. 2011/125725 (or Patent Literature No. 5), and so on. Moreover, devices using capacitances to detect liquid levels are set forth in Japanese Unexamined Patent Publication (KOKAI) Gazette No. 11-311562 (or Patent Literature No. 6), and Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2006-337173 (or Patent Literature No. 7).